1. Field of the Invention
The present invention relates to a sheet processing system that process sheets.
2. Description of the Related Art
Sheet processing apparatuses have been put to practical use. Each sheet process apparatus counts and discriminate sheets of various types. In the apparatus, the sheets placed in the sheet hold unit are conveyed, one by one, to the inspection unit. The inspection unit detects light coming from each sheet and acquires an image based on the light. The sheet processing apparatus first examines the image thus acquired, and then determines whether the sheet is genuine, damaged or unusable. If the sheet is found to be unusable, the apparatus will rejects it. Further, the sheet processing apparatus classifies sheets into groups in accordance with whether they are genuine, damaged or unusable, and collects the sheets, group by group.
Identification data may be printed on each sheet in some cases. For example, Jpn. Pat. Appln. KOKAI Publication No. 2006-293464, a patent publication based on a Japanese patent application, describes a sheet processing apparatus. This apparatus reads the identification data printed on each sheet and changes the reference value used to inspect images in accordance with the identification data.
This sheet processing apparatus shreds any sheet that is damaged too much to be circulated again. Any sheet circulated for a long time since the issuance date is discriminated as a damaged one that should be cut into shreds, though it is not so much damaged. However, the sheet processing apparatus recognizes such a sheet as genuine if the sheet does not appear damaged. Therefore, the sheet cannot be processed as a damaged one as is desired.
If a forged sheet is found, it is demanded that any other sheet printed with the same identification data should be rejected. However, the sheet processing apparatus disclosed in the patent publication cannot confirm the identification data printed on the forged sheet. Consequently, the apparatus cannot reject such a sheet as demanded.